I did notice that the pics you post of the cars you detail were all fairly new / well maintained.
PC noobness:
I had the same concerns as you - screwing up! But after a lot of reading, dummies can use a PC.
Thin waxes:
There are guys using Zaino with the PC, which is just as thin if not thinner than Klasse. It's a matter of learning the technique.
Pc on moulding/trim:
Painter's tape. Easy on, easy off, ease of mind.
PC on older paint:
Did you see the thread of the red car that the paint would come off on your hands when you touched it? Did you see the after pics?

Impossible to get those kinds of results by hand.
How long would it take to get this (before):

To look like this (after):

You can't - it's near impossible. I've tried on dark green with a variety of polishes. You get to a certain level and just can't get it perfect.
That's the advantage of the PC -
results, time, effort and amount of product used.
My PC is in the mail. As soon as I give it a go on the dark green I'll post before and after pics and PM you the link.